And in an increasingly competitive global economy, those variables are changing faster than ever before.

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The Knight Frank survey, scheduled for release Wednesday, ranks global cities based on a number of variables: economic activity, political power, quality of life, education and influence.

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The real challenge is figuring out whether a particular storm or flood was due to climate change or natural variables, said Chris Field, founding director of the Carnegie Institution's Department of Global Ecology.

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Tendai Musikavanhu, president of Old Mutual Global Index Trackers, part of the Old Mutual investment and insurance banking family, says there are too many variables at play to know for sure.

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